Friction reducing

ABSTRACT

REDUCTION OF FRICITION LOSS IN OIL WELL FRACTURING IS ACCOMPLISHED THROUGH THE ADDITION OF SMALL AMOUNTS OF COPOLYMERS OF ACRYLAMIDE AND DIMETHYL DIALLYL AMMONIUM CHLORIDE OR OTHER DIALLY AMMONIUM COMPOUNDS, WITH AND WITHOUT CROSSLINKING BY N,N&#39;&#39; METTHYLENE BISACRYLAMIDE.

United States Patent Ofice Patented Feb. 9, 1971 3,562,226 FRICTION REDUCING Owen C. Gayley, Coraopolis, M. Frederick Hoover, Bethel Park, and Leonard J. Persinski, Pittsburgh, Pa.,

to about 50% by weight acrylamide and the balance derived from monomers of the formula (CH:CH=CH2):

assignors, by mesne assignments, to Calgon Corporation, a corporation of Delaware No Drawing. Continuation of abandoned application Ser.

No. 595,620, Nov. 21, 1966. This application Aug. 13, wherein R and R are independently selected from the 1969, 854,016 group consisting of alkyl groups having one to four car- Int. Cl. C08f /00, 15/40 10 bon atoms US. Cl. 260--80.3 5 Claims CHZCH OH, and CI-I 5-NHz ABSTRACT OF THE DISCLOSURE r The anion of the quaternary monomer is preferably chlo- Redllcnon of fnctlon loss i 011 Well fractunng ride. Some copolymers falling within this description and Comphshed through h addltlofl of amounts methods of making them are disclosed in Schuller & CPOIYmeFS of acrylamide and d1me,thy1 dlanyl l Thomas US. Pat. 2,923,701. A preferred composition is um chlonde or (ilanyl ammonfum Wlth a terpolymer including as a third component about 0.001 Wlthout crosslmkmg by N methylene blsacryl' to 0.006 weight percent of N, N-methylene bisacrylamide. amide.

The polyelectrolytes may be made by conventional re- This is a continuation of application Ser. No. 595,620, dox catalyst systems in solutions of 520% by weight filed Nov. 21, 1966, and now abandoned. of total monomer and may be recovered by various means This invention relates to the art of reducing energy known in the art such as drum drying. Preferably, they loss during the flow of fluids through pipes, which by will be hydrolyzed to the extent of 0.40% of the amide common usage in oilfield terminology has become known groups in the polymer. After drying, they are fully wateras friction reduction. Our invention is particularly disoluble and may be fed directly to the fracturing medium rected to friction reduction in brines and fresh water or other aqueous medium. They may of course be used used in fracturing operations. Without having been dried.

Such polymers as sodium polystyrene sulfonate, poly- A preferred polymer is made from a monomer mixethylene oxide and polyacrylamide have been proposed ture which consists essentially of about 90% acrylamide, for friction reduction in oilfield usage. See US. Pats. about 0.001% to about 0.006% N, N'-methylene bis- 3,023,760; 3,254,719 and 3,102,548 as examples. See acrylamide, and the balance dimethyl diallyl ammonium also, Studies of the Reduction of Pipe Friction with the chloride.

Non-Newtonian Additive CMC," by Riphen and Pelch, To demonstrate the effectiveness of our invention, we a Department of Commerce publication dated April 1963. utilized a laboratory friction loop in which a test fluid Although polyacrylamide has proven satisfactory for is circulated through a pipe having an internal diameter many oilfield installations, there are many others in 40 of about 0.25". Pressure measurements were made at which it and other polymers of acrylamide are unsatispoints about 5 feet apart. In a 2% CaCl brine various factory because of environmental factors such as high concentrations of polymers within our invention were cation content of the fracturing medium or other aqueous added and the friction reduction results were noted. In fluid to be pumped. Polyacrylamide is generally incom- Table I, high molecular Weight polymers were used havpatible with significant quantities of cations. In the presing weight ratios of acrylamide to diallyl dimethyl amence of oilfield brines of the type sometimes used in rnonium chloride of /50, /25, /15 and /10. fracturing operations, which frequently contain total dis- These in turn were either unhydrolyzed or hydrolyzed solved solids in the range of up to 300,000 p.p.m., they 15%. In the table, the notation 50/50 means a copolybecome insolubilized. Shear stability is also greatly remer having even eight proportions of acrylamide and diduced. Particularly difficult are brines having alkaline methyl diallyl ammonium chloride. 85/15 means 85 earth metal contents of more than 1000 p.p.m. It is not 50 weight percent acrylamide and 15 percent dimethyl diallyl uncommon for an oilfield brine useful as a fracturing ammonium chloride; 90/10 means a ratio of acrylamide medium to contain at least 5000 parts per million of to dimethyl diallyl ammonium chloride of 90 to 10. The calcium. terms 0% hydr. and 15% hydr. refer to the per- Throughout this specification, when we speak of brine centage of the number of amide groups which were hystability, we mean the property of remaining effective drolyzed. The notation 75/25 means 75% acrylamide and as a friction reducer in media containing at least 2% 25% dimethyl diallyl ammonium monomer. In each case, total dissolved solids, of which at least 5000 ppm. are ml. of a 2% solution Was introduced into the loop polyvalent cations. However, our invention is useful not containing 10 liters of the previously described brine. only in brines but in any aqueous fracturing medium. Results in the tables are given in terms of the precent Our brine stable polymers are copolymers of 99.9% 60 reduction of friction.

TABLE I F/ R at X minutes Maximum friction I Polymer reduction 5min. 10 min. 15 min. 20 min. 25 mm. 30 mm.

50/50, 0% hydr 58.4 at 30 seconds 45. 0 52.2 at 30 seconds. 41. 0 55.4 at 30 seconds. 47. 0 68.2 at 30 seconds. 66. 7 59.3 at, 30 seconds. 56.0 65.5 at 0 seconds 64. 0 67.0 at 0 seconds 62. 5 90/10, 5% hydr 49.6 at 0 seconds 41. 9

We have also found that as much as 0.006 weight percent of N, N-methylene bisacrylamide may be added to a monomer mix to prepare copolymers otherwise within the descriptions previously disclosed. We prefer not to use more than about .006% N, N'-bisacrylamide.

A series of tests was run on two crosslinked polymers of differing diallyl dimethyl ammonium content. Polymer A was made from a monomer batch mix of about 98.5% (by weight) acrylamide and about 1.5% dimethyl diallyl ammonium chloride, to which was added 0.004% N, N'-methylene bisacrylamide; Polymer B consisted of about 95.0% acrylamide and about 5.0% dimethyl diallyl ammonium chloride to which was added 0.004% N, N'-methylene bisacrylamide. They were hydrolyzed to the various degrees shown in Tables II and III and tested in the friction loop in the various media indicated in the tables with the results shown.

TABLE II [Friction reduction of 240 p.p.m. solution of Polymer A] Percent Maximum F/R at F/R at F/R at Fluid hydrolysis Fl 5 min. 10 min. 15 min.

Tap water 66. 8 64. 5 60. 5 57. 27 71. 71. 0 71.0

2% CaClz 66. 2 64. 8 61. 0 57. 0 27 69. 0 59. 0

% NaCl 67. 4 66. 4 63. 4 59. 0 27 70. 3 68. 5 65. 6 60. 0

1 Base.

TABLE III [Friction reduction of 240 p.p.m. solution of Polymer B] Percent Maximum F/R at F/R at F/R at Fluid hydrolysis F/ 5 min. 10 min. min.

Tap water 66. 0 61. 8 55. 8 19 72. 0 70. 7 71. 0 69. 9

2% OaOl 68. 1 63.0 56. 4 52. 2 19 67. 9 54. 1 46. 6

10% NaCl 68. 8 65. 1 69. 2 54. 2 19 71. 0 68. 8 65. 8 61. 4

1 Base.

It is apparent from the above presented data that our polymers are effective to different degrees with and without hydroylsis. However, we prefer to use polymers having about 10 to about 40% of the amide groups hydrolyzed. The friction reducing polymers are normally used in amounts from about 100 p.p.m. to 500 p.p.m., but 1000 ppm. or over may be used without significant losses in efficiency due to viscosity. There appears to be no minimum concentration below which they are completely without effect; a very small amount is elfective to a very slight degree. The cross-linking effected by a concentration of from 0.002% to 0.006% N,N'-methylene bisacrylamide is desirable because it increases the apparent chain length of the polymer without sacrificing solubility. Concentrations above 0.006%, when fully incorporated into the polymer, will tend to cause gelling. Concentrations below 0.002% are useful but do not cause a significant change over the corresponding uncrosslinked polymer.

We do not intend to be limited to the particular examples and illustrations described above. Our invention may be otherwise practiced within the scope of the following claims:

We claim:

1. Method of reducing friction loss due to turbulent [How of aqueous fracturing fluid in an oilfield fracturing process comprising adding to said fracturing fluid a random, addition, water-soluble copolymer of (a) acrylamide, (b) a monomer of the formula R (oHFoE-orrnm where R and R are independently selected from the group consisting of alkyl groups having one to four carbon atoms, CH CH OH, and

and (c) up to about 0.006 weight percent of N,N'-methylene bisacrylamide, wherein the weight ratio of acrylamide to monomer of the formula is from about 1:1 to about 99910.1, in an amount sufficient to reduce friction loss,

2. Method of claim 1 in which the diallyl monomer is dimethyl diallyl ammonium chloride.

3. Method of claim 1 in which the amide groups in the polymer are hydroylzed from 10 to 40%.

4. In the process of fracturing an earth formation penetrated by a well, wherein an aqueous fracturing fluid is injected through the well into the earth formation at a high velocity to cause fracturing of the formation, the improvement of decreasing the friction loss in the flow of the aqueous fracturing fluid which comprises adding to the fracturing fluid 0.005 to 0.5 weight percent of a random, addition, water-soluble copolymer made from a monomer mix consisting essentially of, by weight, (a) at least 50% acrylamide, (b) up to about 0.006% N,N- methylene bisacrylamide, and (c) at least 0.1% dimethyl diallyl ammonium chloride, and injecting the resulting mixture in the well.

5. A random, cross-linked, addition, water-soluble polymer made from the vinyl polymerization of, by weight, (a) at least 50% acrylamide, (b) from 0.002% to about 0.006% N,N-methylene bisacrylamide, and (c) at least 0.1% dimethyl diallyl ammonium chloride.

References Cited UNITED STATES PATENTS 2,923,701 2/1960 Schuller et al. 3,147,218 9/1964 Booth et a1. 3,252,904 5/ 1966 Carpenter.

JOSEPH L. SCHOFER, Primary Examiner S. M. LEVIN, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 562, 226 Dated February 9 1971 Inventor) Owen C. Gayley et 3.1.

It is certified that error appears in the abovev identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 5, before "bisacrylamide" insert methylene Signed and sealed this 23rd day of May 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patent 

